Boeing’s Biggest 747 To Fly With Empty Tail Tanks

Boeing will deliver its newest, biggest airplane soon, but the behemoth won’t fly quite as far as the company hoped.

The new 747-8 Intercontinental is the passenger version of Boeing’s biggest jumbo jet, and a problem discovered in testing means customers can’t use the fuel tanks in the horizontal stabilizers — at least not yet.

Like many large airliners, the 747 has fuel tanks in many places. The new 747-8, like its predecessor, the 747-400, carries about 3,300 gallons of fuel in the horizontal part of the tail. But customers won’t be able to fill those tanks after a problem was discovered when the tail tanks were more than 15 percent full according to Flightglobal.

Instead, a section of the fuel line that feeds fuel to the tail tanks will have to be removed. Boeing is working on a solution and the restriction is expected to be lifted eventually. The Intercontinental carries a total of 63,055 gallons of jet fuel; barring use of the tail tanks will cut range by 300 to 400 miles.

The horizontal tail surfaces of the 747-8 have the capacity to carry 3,300 gallons of fuel.

The problem was found during a computer simulation to demonstrate the potential failure of a mounting strut connecting an engine to the wing. When the failure was simulated, the weight of the fuel in the tail created a flutter problem in the wing. Boeing says this type of failure has never actually occurred on a 747, but the potential for flutter must be addressed.

Lufthansa, the launch customer for the 747-8 Intercontinental, told Flightglobal it doesn’t expect the reduced range to immediately affect the company’s plans for the new airliner. Airliners often fly with less than full tanks and the decreased range should affect only those routes at the maximum range of the plane. One side effect however may be a loss in efficiency because losing roughly 20,0000 pounds of fuel will change the plane’s center of gravity.

The freighter version of the 747-8 which has been in service since October does not use the tail tanks because customers prefer the greater hauling capacity over extended range.

Boeing is expected to deliver the first 747-8I to a private customer next month, and the first for scheduled airline service with Lufthansa in March.

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